1. Field of the Invention
The present invention relates to an air induction system of an internal combustion engine. More particularly, the invention relates to varying the length of an intake pipe of an air intake system of an engine. The invention also relates to varying the intake volume of the intake system of the engine.
2. Discussion of Related Art
As is conventionally known, combustion engines take in air to mix with fuel to provide the combustion that fires the engine. Performance of combustion engines can be varied by changing a number of variables, including the amount of air taken in and the path through which the air travels. One way to enhance engine performance is to increase the volume of air taken in by the air intake system. Another way to enhance performance is to reduce resistance experienced by the air in the air intake system. It is known that extending intake ducts can provide an engine with higher torque at a lower speed. However, at higher speeds it is more desirable to have shortened intake ducts to gain more power.
One prior art method of modifying an air intake or induction system to enhance performance is disclosed in DE 38 20 674 A1, in which the length of individual intake pipes can be varied continuously by moving the pipe elbows in and out telescopically while guided in stationary intake manifolds. During a low rotational speed of the internal combustion engine, these individual intake pipes are at their maximal length and their inlet openings rest against an interior wall of a suction distributor that surrounds the pipe elbows. In this position, the suction distributor supplies air to the individual intake pipes by way of a pipe connected thereto. When the rotational speed of the engine increases, the pipe elbows are swivelled into the intake manifolds so that the inlet openings lift away from the interior wall and the individual intake pipes take air in directly from the suction distributor.
Similar devices are known from the U.S. Pat. No. 5,143,026A and EP 0 747 584 A1, where pipe elbows are held in the air collector in an open condition on a stationary shaft so that they can be swivelled into different positions. In the first position, one outlet opening of the pipe elbow rests directly on an inlet opening of the intake manifold. As a function of the rotational speed and/or the load, in the first position, the intake path is formed relatively long by the intake manifolds and the pipe elbows. This results in an increase of the engine torque at low engine speed. In a second position of the pipe elbows, the intake manifolds take air in directly from the air box, which results in more power at high engine speeds.
These prior art devices require additional room to effect movement and involve several moving parts in often complicated operations.